Here I work on the same material from Daily Practice 10 but only in one key (concert A major 7 #5). Using space, focusing on posture, balance and breath will allow you to cultivate many good habits while repeating a phrase in order to help develop your technique. I believe that one very real danger in repetition lies in the habits you are unaware of that you bring into your process. If you are unaware that while repeating a phrase over and over you are also may be practicing mistakes, playing with tension, playing with a wondering (thinking) mind, poor time, non-listening, poor posture, shallow breathing, lack of space etc. you will inadvertently be sabotaging your ability to perform and play well with others even though you are spending hours working on the art form.